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Transcript
2-7 Diffusion 1 Molecules Molecules are the smallest part of a substance that still have the characteristics of that substance. Molecules are always moving 2 Diffusion is.. Movement of material from an area where molecules are crowded to an area where they are less crowded. http://commons.wikimedia.org/wiki/File:Diff usion.gif 3 Passive Transport Is diffusion through cell membranes http://www.bio.miami.edu/~cmallery/150/m emb/c8.7x11.diffusion.jpg 4 OSMOSIS Osmosis is the movement of water molecules through a membrane Many substances dissolve in water. Water plus the dissolve substance move through the cell membrane http://www.stjohn.ac.th/Department/school/bi o_pix/osmosis.gif 5 What do you think? What would happen if water constantly entered a cell, and none left it? 6 It will burst 7 Active Transport The cell may need more of a substance inside the cell than outside. This requires molecules to move in the opposite direction they would normally move. Energy is required for molecules to move from less crowded to more crowded areas. http://www.biology4kids.com/files/art/cell2_ active1_240x180.gif 8